JP2815892B2 - Emulsion composition for paper coating - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an emulsion composition for paper coating suitable as a paper coating agent. More specifically, the present invention relates to an emulsion composition for paper coating in which a specific organosilicon compound is blended to significantly improve the adhesive strength without impairing the inherently preferable physical properties.

(Prior Art) A paper coating liquid (color) for applying a pigment to improve physical properties of paper is widely used in the field of paper coating.
Such paper coating liquids usually contain a binder for bonding the pigments to each other or the pigment and the object to be coated, and various kinds of binders have been proposed depending on the purpose of use. Among them, typical ones are a polymer emulsion and an aqueous binder. As the polymer emulsion, a styrene-butadiene polymer emulsion is mainly used, and as the aqueous binder, starch, casein, or the like is used.

In order to improve the adhesive strength of polymer emulsions, adjustment of the amount of styrene-butadiene used, addition of a third monomer, and selection of the particle size have been performed. In many cases, the improvement of the molecular weight is accompanied by a decrease in other physical properties such as blister resistance, rigidity and halftone dot reproducibility, and it has been difficult to obtain a polymer emulsion in which all the required physical properties are balanced.

On the other hand, it has been proposed to add a certain kind of organosilicon compound to a carboxylated rubber latex to improve the adhesive strength between metal and wood (Japanese Patent Application Laid-Open No. 53-102342). Has the disadvantage that it must be added immediately before use, since it causes gelation of the latex.

(Problems to be Solved by the Invention) The present invention overcomes the drawbacks of the conventional polymer emulsion for paper coating as described above, and has good blister resistance, rigidity and halftone dot reproducibility, and It is an object of the present invention to provide a paper coating emulsion composition that gives a coating film having significantly improved adhesive strength.

(Means for Solving the Problems) The present inventors have conducted intensive studies on an emulsion composition for paper coating suitable for use in the paper coating field, and as a result, have found that a polymer emulsion has a specific composition. By blending the organosilicon compound having a chemical structure in a specific ratio, an emulsion composition for paper coating that can form a coating film having high blister resistance, rigidity, good dot reproducibility, and high adhesive strength is obtained. And the pH of the paper coating emulsion composition
Was adjusted to 3 to 6.5, and it was found that the performance could be maintained for a long time, and the present invention was accomplished based on this finding.

That is, the present invention provides a polymer emulsion having the formula Wherein R and R 'in the formula are a hydrogen atom, an alkyl group having 1 to 7 carbon atoms or an alkoxyalkyl group. 0.01 to 20% by weight of an organosilicon compound having a group represented by the following formula:
(In terms of solid content) is added after the polymerization of the polymer emulsion, and the pH is from 3 to 6.5, thereby providing an emulsion composition for paper coating.

The polymer emulsion used in the present invention is an emulsion using water as a dispersion medium. The production method is not particularly limited, and conventionally known methods can be used in addition to emulsion polymerization, dispersion polymerization, and suspension polymerization, and styrene-butadiene-based, styrene-acryl-based, acrylic-based, ethylene-vinyl acetate-based, Examples include vinyl acetate-acrylic, vinyl acetate-based, vinylidene chloride-based, and natural rubber-based latex. These polymer emulsions may contain a functional group such as a carboxyl group, a hydroxyl group, an N-methylol group, an amide group, a glycidyl group or a sulfonic acid group.

In the production of such a latex, a monomer having polymerizability is used, and examples thereof include styrene,
Aromatic (di) vinyl compounds such as α-methylstyrene, chlorostyrene, alkylstyrene and divinylbenzene (here, the characters in parentheses may or may not be read. The same applies hereinafter. .) Methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, hydroxyethyl (meth) acrylate, glycidyl (meth) acrylate, ethylene Glycol di (meta)
(Meth) acrylates such as acrylates,
Nitrile monomers such as acrylonitrile and methacrylonitrile; vinyl esters such as vinyl acetate; vinyl halides such as vinyl chloride and vinylidene chloride; (meth) acrylamide; ethylenic such as N-methylol (meth) acrylamide Amide monomers, diene monomers such as butadiene, isoprene, and chloroprene; ethylenic amine monomers such as aminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, and diethylaminoethyl (meth) acrylate; fumaric acid, itaconic acid, and maleic acid And ethylenically unsaturated carboxylic acids such as (meth) acrylic acid. Among them, a polymer emulsion modified with a carboxyl group is particularly preferable. The polymer emulsion in the present invention is not limited to one kind of polymer, and may be a mixture of two or more kinds. Further, it may have alkali thickening.

If the specific production method of the polymer emulsion is described in the example of emulsion polymerization, the above-mentioned single monomer may be used in the presence of an emulsifier, a polymerization initiator, and, if necessary, a molecular weight modifier, a chelating agent, a pH adjuster, and the like. The body may be emulsion-polymerized by setting an appropriate temperature and a polymerization time. The particle size of the polymer emulsion thus produced is usually 0.05 to 1 μm, and the solid content is 40 to
65%.

As the organosilicon compound blended in the present invention, a group in which two or more hydroxyl groups or alkoxy groups are bonded to one silicon atom, that is, a general formula, (Wherein R and R 'are a hydrogen atom, an alkyl group having 1 to 7 carbon atoms or an alkoxyalkyl group).

Particularly preferred among such organosilicon compounds are:
General formula (Wherein R1 is an alkyl group or alkoxy group or alkoxyalkyl group having 1 to 7 carbon atoms, R2 and R3 are alkoxy group or alkoxyalkyl group having 1 to 7 carbon atoms,
(However, at least two or more of R1 to R3 are an alkoxy group.) N is an integer of 0 or 1 to 10, X is a hydrogen atom,
A glycidyl group, a (meth) acryloxy group, a vinyl group, a halogen atom, a hydroxyl group, a thiol group, an amino group, a phenylamino group, an epoxycyclohexyl group, or an aminoalkylamino group. ).

Examples of such organosilicon compounds include γ-
((Meth) acryloxypropyl) trimethoxysilane, vinyltris (β-methoxyethoxy) silane, vinyltriethoxysilane, vinyltrimethoxysilane,
γ-((meth) acryloxypropyl) dimethoxyethoxysilane, γ-((meth) acryloxypropyl) diethoxymethoxysilane, γ-((meth) acryloxypropyl) triethoxysilane, γ-((meth) acryl Roxyethyl) trimethoxysilane, γ-((meth) acryloxyethyl) dimethoxyethoxysilane, γ-
((Meth) acryloxyethyl) diethoxymethoxysilane, γ-((meth) acryloxyethyl) triethoxysilane, γ-((meth) acryloxymethyl) trimethoxysilane, γ-((meth) acryloxymethyl ) Dimethoxyethoxysilane, γ-((meth) acryloxymethyl) diethoxymethoxysilane, γ-((meth) acryloxymethyl) triethoxysilane, β- (3,4
-Epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ
-Glycidoxypropylmethyldiethoxysilane, N-
β (aminoethyl) γ-aminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ- Mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, n-propyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, vinyltriacetoxysilane, dimethyldimethoxysilane, γ -Chloropropylmethyldimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, hydroxypropyltrimethoxysilane, γ-dibutylaminopropyltrimethoxysilane, dimethyldiethoxysilane, - decyl trimethoxysilane, isobutyl trimethoxysilane can be exemplified.

The paper coating emulsion composition according to the present invention is a water-dispersed emulsion containing the polymer emulsion and the organosilicon compound. The organosilicon compound is 0.01 to 20% by weight in terms of solid content based on the polymer emulsion,
Preferably, it must be blended at a ratio of 0.1 to 10% by weight. If the amount is less than 0.01% by weight, the adhesive strength is not sufficiently improved, and if the amount is more than 20% by weight, not only does the adhesive strength not increase, but also the fluidity of the emulsion composition for paper coating. Other physical properties tend to deteriorate.

In the paper coating emulsion composition of the present invention, if necessary, various commonly used additives, for example, a dispersant, a lubricant, an antifoaming agent, a preservative, a waterproofing agent, an antioxidant, and the like. It can be contained. The solid content of the paper coating emulsion composition is usually 40 to 65% by weight,
Preferably it is 45 to 55% by weight.

The pH of the emulsion composition for paper coating of the present invention is 3 to 6.
Must be 5. When the pH of the paper coating emulsion composition is higher than 7.5, there is a possibility that a problem may occur in its own storage stability or the like depending on the type of the organosilicon compound.

The method for producing the paper coating emulsion composition of the present invention,
From the viewpoint of the stability of the organosilicon compound, a method of adding the organosilicon compound to the polymer emulsion after the completion of the polymerization is adopted. Specifically, for example, after completion of the polymerization, the organosilicon compound may be added little by little while sufficiently stirring the stripped polymer emulsion. Also. Depending on the organosilicon compound, it may be preferable to dissolve it in water before adding it to the polymer emulsion and then add it.

In any case, the emulsion composition for paper coating to be produced must be prepared so that the pH is 3 to 6.5. As the pH adjusting agent, caustic potash, caustic soda, ammonia and the like are usually used.

The emulsion composition for paper coating of the present invention is usually prepared as a paper coating liquid and used for coating paperboard, general high quality paper, medium quality paper, gravure paper and the like.

Preparation of paper coating liquid, clay, pigments such as calcium carbonate, dispersant, paper coating emulsion composition of the present invention, other binders and other additives that are optionally added thereto, as appropriate This is done by mixing. The emulsion composition for paper coating is usually used in an amount of 5 to 30 parts by weight based on 100 parts by weight of the pigment. In the dispersion medium of the paper coating liquid,
Usually, water is used and the total solids concentration is 30-75% by weight, more preferably 40-75% by weight.

In applying such a paper coating liquid to the paper,
Any known method such as a size press coater, a roll coater, an air knife coater, and a blade coater is employed. The coating amount is wide depending on the purpose and is not particularly limited, but the solid content is usually about 0.1 to 30 g / m ² .

(Effects of the Invention) The paper coating emulsion composition of the present invention has extremely high adhesive strength and wet strength, and also has a good balance between adhesive strength and blister resistance, and a good balance between adhesive strength and halftone dot reproducibility. When used for paper coating, it gives coated paper with extremely good physical properties such as printability. In addition, such performance can be maintained for a long period of time. Therefore, it has much improved properties as compared with a conventional emulsion composition for paper coating, and is suitable as a coating composition for paper coating.

Next, the present invention will be described in more detail with reference to Examples.
The present invention is not limited in any way by these examples.

In addition, each physical property in coating paper manufacture and other physical properties were calculated | required according to the following method.

(1) Color viscosity The color viscosity was measured at 60 rpm using a Brookfield type (B type) viscometer. It was measured at 4400 rpm by a Hercules type viscometer.

(2) Blank paper gloss was measured at 75-75 ° using a gloss meter.

(3) Ink gloss Use 0.3 ml of ink [New Bright G indigo, manufactured by Toyo Ink Co., Ltd.] for the coated paper sample, print it with a printing tester, adjust the humidity all day and night, and use a gloss meter to measure the amount of ink. Measured at −60 °.

(4) Printability Using a printing tester, dry strength, wet strength, inking property, water absorbency, and ink set were measured using an ink having an appropriate tack, and evaluated on the following four levels.

◎: Very good ○: Good △: Somewhat poor ×: Very poor (5) Blister resistance Coated paper which has been coated on both sides and calendered is printed with a yellow ink using an RI printing machine manufactured by Akira Seisakusho Co., Ltd. (0.3cc) Double-sided solid printing is used as a sample. This sample was immersed in a heated oil bath, and the temperature at which blisters were generated was read and evaluated as follows.

 ：: No blisters were generated at all. ○: Blisters were slightly generated. Δ: Blisters were considerably generated. ×: Blisters were generated over the entire surface.

(6) Halftone dot reproducibility Number of missing halftone dots using Ministry of Finance gravure printing press
It was expressed by.

(7) Particle size of polymer emulsion (μm) The polymer emulsion was treated with osmic acid, which was magnified 30,000 times with a scanning electron microscope, and the diameter of 500 particles in the obtained micrograph was measured. , The number average.

(8) Gel content (% by weight) The polymer emulsion was thinly flowed on a glass plate in an atmosphere of a temperature of 23 ° C. and a humidity of 65% and dried for 24 hours to form a film. The sample was collected into a screw tube, 30 ml of toluene was added thereto, and the mixture was treated with a shaking machine for 3 hours. Then, a 325 # stainless steel wire mesh (size: 5 × 5
× 5 cm) was transferred onto a screw tube, washed with 5 ml of toluene, dried in a dryer at 130 ° C. for 1 hour, and the toluene-insoluble content was measured.

Example 1 Preparation of emulsion composition for paper coating of the present invention 120 parts by weight of water was added to an autoclave equipped with a dropping device and a stirring machine.
0.2 parts by weight of sodium alkylbenzenesulfonate, 2 parts by weight of fumaric acid and 1.2 parts by weight of a styrene-acrylic acid modified seed latex (number average particle diameter 0.03 μm) are charged. Next, a mixture of 60 parts by weight of styrene, 28 parts by weight of butadiene, 10 parts by weight of methyl methacrylate, and 5 parts by weight of carbon tetrachloride, 30 parts by weight of water, 1.2 parts by weight of potassium persulfate,
0.1 parts by weight of sodium alkylbenzenesulfonate and 0.3 parts by weight of caustic potassium were separately prepared, and each was separately added at a polymerization temperature of 80 ° C. for 6 hours. Then it was kept for 2 hours. The polymerization rate of the polymer emulsion (A) thus prepared was 99%, the number average particle diameter was 0.18 μm, and the gel content was 45%. Immediately after stripping, the pH of the polymer emulsion (A) was adjusted to 5.5 by adding caustic soda to γ.
-Glycidoxypropyltrimethoxysilane was added at 2% by weight in terms of solid content and sufficiently dispersed to obtain an emulsion composition for paper coating.

Preparation of the composition for paper coating Using the emulsion composition for paper coating prepared above,
After preparing a composition having a color composition shown in Table 1 (solid content: 61% by weight), the composition was adjusted to pH 9 with an aqueous ammonia solution to obtain a coating composition.

The viscosity of the coating composition was measured, and then applied to both sides of a commercially available high-quality paper at 14 g / m ² (one side) using a blade-type continuous winding coating machine. In addition, using a super calender at 50 ° C and 150 kg / cm, 2 per side
I passed each time. The printing properties of the coated paper thus produced were evaluated, and the results are shown in Table 3.

Comparative Example 1 A coated paper was produced in the same manner as in Example 1 except that γ-glycidoxypropyltrimethoxysilane was not added to the polymer emulsion (A) of Example 1. Table 3 shows the results of evaluation of this coated paper in comparison with Example 1.

Example 2 Example 1 was repeated except that in place of the monomer, 50 parts by weight of styrene, 38 parts by weight of butadiene, 5 parts by weight of ethyl acrylate, 5 parts by weight of acrylonitrile, and 2 parts by weight of itaconic acid were used. Polymer emulsion (B) was prepared in the same manner as polymer emulsion (A). The polymerization rate of the polymer emulsion (B) thus prepared was 99%, the number average particle diameter was 0.15 μm, and the gel content was 85%. This polymer emulsion (B) is used in place of (A), and γ
A coated paper was produced in the same manner as in Example 1 except that γ-methacryloxypropyltrimethoxysilane was used in place of glycidoxypropyltrimethoxysilane at 2% by weight in terms of solid content. Table 3 shows the evaluation results.

Comparative Example 2 A coated paper was produced in the same manner as in Example 2 except that γ-methacryloxypropyltrimethoxysilane was not added to the polymer emulsion (B) of Example 2. Table 3 shows the results of evaluation of this coated paper in comparison with Example 2.

Example 3 1% by weight of γ-methacryloxypropyltriethoxysilane was added to an alkali thickening type latex (latex L-1295, manufactured by Asahi Kasei Corporation, pH 5.7) in terms of solid content, and the results are shown in Table 2. A coated paper was produced in the same manner as in Example 1 except that the blending was used. Table 3 shows the evaluation results.

Comparative Example 3 A coated paper was produced in the same manner as in Example 3 except that γ-methacryloxypropyltrimethoxysilane was not added to L-1295 of Example 3. Table 3 shows the results of evaluation of this coated paper in comparison with Example 3.

Example 4 The paper coating emulsion composition prepared in Example 1 was used for 20 times.
A coated paper was produced in the same manner as in Example 1 except that 30 days had passed at ℃. Table 3 shows the evaluation results.

Comparative Example 4 A coated paper was produced in the same manner as in Example 1 except that the pH of the emulsion composition for paper coating was set to 8 and that the temperature was changed to 30 days at 20 ° C. Table 3 shows the results of evaluation of this coated paper in comparison with Example 4.

Comparative Example 5 A coated paper was produced in the same manner as in Example 1, except that the blending amount of γ-glycidoxypropyltrimethoxysilane in Example 1 was changed to 25% by weight in terms of solid content. Third evaluation result
It is shown in the table.

Claims (1)

(57) [Claims] 1. A polymer emulsion having the formula Wherein R and R 'in the formula are a hydrogen atom, an alkyl group having 1 to 7 carbon atoms or an alkoxyalkyl group. 0.01 to 20% by weight of an organosilicon compound having a group represented by the following formula:
(Equivalent to solid content) after the polymerization of the polymer emulsion, and the pH is 3 to 6.5.